i68 CHAPTER IX 



6. The fibrovascular bundles are tinted red. 



7. Subterraneous outbranchings are formed. 



8. The sheath and root buds turn vermilion. 



9. In some cases there is no formation of wax on the stem. 



10. The growing part of the stalk is frequently dyed red. 



11. The leaf sheath and stalk stick together. 



12. There is an accumulation of secondary organisms. 



The presence of gum in sereh is a point about which much has been 

 written. The major portion of opinion seems to be that the presence of 

 gum is a consequence of and not directly connected with the disease, since, 

 if the gum is of bacterial origin, the growth of the bacteria might only take 

 place in cane already weakened by disease. 



A red coloration of the fibrovascular bundles is a characteristic of 

 sereh. This coloration is most pronounced at the node, but often ap- 

 pears in the internode as a red stripe.* This appearance is quite distinct 

 from the red patch with white centre characteristic of the red rot of 

 the stem. 



The very large amount of work that has been done on sereh has up to the 

 present failed to elucidate the cause of the disease, unless the identification 

 by Wolzogen-Kiihr with gumming is confirmed. Opinion is divided in 

 ascribing the cause to physiological and to pathological causes. Amongst 

 the first named have been suggested bad drainage, injudicious manuring, 

 late planting, excessive ratoonage, an insufficiency of silica in the soil and 

 degenerescence. 



As regards parasites, Treub^"^ ascribed the disease to the attacks of a 

 nematode worm, which he named Heterodera javanica. Coinciding with the 

 attacks of the worm he observed the presence of a fungus of the genus 

 Pythium. Treub believed that the nematode penetrated the bark of the 

 root at places of accidental injury or at the growing point, After having 

 arrived within the root the worm worked its way parallel to the central axis 

 until it arrived at the point of growth of a lateral root. SoltwedeP"' also 

 attributed the damage to attacks of a worm, which he named Tylenchus 

 sacchari, stating that the parasite passed its existence in the root, which it 

 destroyed. 



The connection between sereh and nematode worms is not now accepted. 

 Janse'^'^^ ascribed the cause of sereh to two organisms, Bacillus sacchari 

 and Bacillus glangce, and stated that these organisms attack plants other 

 than the cane. He considered that the seat of the disease lay in the red- 

 coloured fibrovascular bundles. The dependency of sereh on these organ- 

 isms is not now accepted. 



Went^*'^ considered sereh as a combined leaf sheath and root disease 

 caused by an organism Hypochrea sacchari, the description of which is as 

 follows : — 



Pulvinata, deinde depressa, carnosa, pallide fusca, stromatibus 2-4 m.m. lat. 

 I m.m. crassis, saepe leviter collascentibus, intus pallentibus vel albidis, peritheciis 

 fuscis, ostiolis vix prominulis, 200-500 x 150-200, ascis linearibus breve pedicellatis, 

 100 X 5, sporidiis monostichis 8, e cellulis duabus inaequalibus, mox decedentibus 

 compositis, cellula superiori globosa 4 diam., cellula inferiori cuboidea oblonga 6x4, 

 fumose olivaceis. Conidiis = Verticillium sacchari. 



In Fig. 70 is shown, after Went, an ascus of the Hypocrea containing 

 eight spores. 



* A red striping of the sugar cane associated with the presence of gum has also been described by Greig Smith 

 in Australia. This he ascribed to the association of an unidentified ascomycete with a slime-producing bacillus, 

 to which he gave the name of Bacillus pseudarabinus. 



